Listeria Interventions: Processing

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Listeria Interventions Processing

• Lynn Knipe
• The Ohio State University

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Processing Interventions

• Product Formulations
• Post-Packaging Pasteurization

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Product Formulations

• Some products will not support growth of L.
  monocytogenes
• High acid content (pH lt 4.5)
• Fermented products (lactics)
• Low water activity (lt 0.90)
• High salt levels

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Product Formulations

• Organic Acids
• Smoke liquid or natural
• Spices natural resins, oleoresins
• preservatives
• bacteriocins

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Organic Acids

• 4.8 sodium and/or potassium lactate and 0.25
  sodium diacetate approved as antimicrobial
  agents in meat products.
• Synergistic effect of lactates and diacetates in
  inhibiting growth of L. monocytogenes in meat
  products.

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Organic Acids

• Effective when added to formulations, but not
  as a dip.
• 2-3 sodium lactate without flavor problems.
• gt0.12 sodium diacetate can result in vinegar
  flavor.

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Smoked Products

• Both natural liquid effective.
• Phenols and acetic acid most antilisterial.

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Preservatives

• High levels of sodium benzoate, propyl paraben,
  potassium sorbate.
• More effective at lower pH and temperatures
• BHA, BHT, TBHQ effective.
• Limited approval for use in meat products.

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Bacteriocins

• Natural polypeptides from bacteria that inhibit
  other bacteria.
• Nisin pediocin (lactics) inhibit L. mono.
• Only Nisin approved and commercially available
  on large scale.

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Post-Packaging Heat/Pasteurization

• Heat re-applied to package surfaces to destroy
  any surface cross contamn.
• Immerse pkg. in hot water (185 for 8 min.)
• Surface steam (205F, 15 sec)
• Hot air or infrared.

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Post-Packaging Heat Disadvantages

• Difficult to heat all surfaces
• May adversely affect package.
• Product changes with heat (color, texture,
  purge, etc.)
• Expensive
• Apply heat/moisture in ref. room (condensation,
  etc.)

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Individually-Wrapped Products are Easiest to
Post-Package Pasteurize/Heat
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Cook-in-the-Bag Processing

• Listeria contamination is not likely to occur
  as long as package is not opened and exposed to
  the environment.
• Listeria contamination could occur at the point
  that final user opens the package.

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Non-Thermal Post-Packaging Treatments

• High Pressure (HPP)
• Expensive, batch process - OSU
• Pulsed Electric Field (PEF)
• better with fluid products, OSU
• Ultraviolet (UV) Light Lm resistant, surface
  effect only
• Electrolyzed oxidizing water
• some promise, not near term

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Irradiation

• Post-package destruction of Lm at relatively
  low doses.
• 0.05-0.11 per pound
• Product changes are minimal
• (rancidity may be increased).
• Not approved for RTE products.
• Consumer acceptance still unknown.

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Conclusions

• Lag phase extended with anti- microbials, but
  zero tolerance.
• Lactates and acetates used.
• Post-pkg. pasteurization commercially
  practiced.
• Irradiation is not a simple solution.
• Increased costs, product changes inevitable.